Highly sensitive simultaneous electrochemical determination of reduced and oxidized glutathione in urine samples using antimony trioxide modified carbon paste electrode

Abstract

A simple and reproducible electroanalytical sensor using antimony trioxide modified-carbon paste electrode (Sb2O3–CPE) as sensing element was employed for the first time for simultaneous determination of glutathione (GSH) and glutathione disulphide (GSSG). The electrochemical response of Sb2O3–CPE was characterized by cyclic voltammetry and square-wave voltammetry. Scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM) and Raman mapping were used to characterize the morphology and surface modification. A significant enhancement in the peak current response of GSH and GSSG accompanied with a good separation of the peaks were obtained at the modified electrode compared to the bare CPE. GSH and GSSG exhibited well-defined oxidation peaks at +1.08 V and +1.36 V (vs. Ag/AgCl, 3 mol/L) in Britton-Robinson buffer at pH 6.0. Parameters such as used supporting electrolyte and its pH value, amplitude and frequency were optimized for square-wave voltammetric determination. Under optimal conditions, voltammetric responses were linear in the concentration range of 2–200 μmol/L for GSH and GSSG. The limits of detection were 0.34 μmol/L and 0.10 μmol/L for GSH and GSSG, respectively. Moreover, the proposed sensor also showed good reproducibility, stability and selectivity. Finally, the proposed sensor was applied for the simultaneous determination of GSH and GSSG in urine samples with satisfactory results.